1. Field of the Invention
The present invention relates to an electro-photographic image forming device. More particularly, the present invention relates to an electro-photographic image forming device that is capable of controlling a print speed and a method for controlling the same.
2. Description of the Related Art
Examples of an image forming device employing an electro-photographic scheme may include a copy machine, a laser beam printer (LBP), a light emitting diode (LED) printer, a plain paper facsimile, and so forth.
The electro-photographic image forming device performs a print operation for printing a predetermined image on a record sheet through a series of photo-transfer processes consisting of electrification, exposure, development, transfer, fixing, and delivery. Hereinafter, an LBP will be used as an example for providing a description of such conventional devices.
A print engine of the LBP is comprised of an engine driving system for driving a photosensitive drum, a developing unit, a fixing unit or the like, and a laser scanning unit (LSU) driving system for driving the LSU. A print speed of the LBP is determined by the performance of the engine driving system and the LSU driving system. A driving speed of the LSU driving system is determined by a driving speed of the engine driving system. That is, the print speed of the LBP is determined by a diameter of the photosensitive drum, a development processing speed of the developing unit, a number of polygon mirror planes, a rotating speed of a polygon motor for driving the polygon mirror, and so forth.
As such, in order to enhance the print speed in a state wherein the performance of each component is already determined, the driving speed of the engine driving system or the driving speed of the LSU driving system should be increased. However, there is some difficulty in enhancing the performance due to a limit of the performance already given for each driving system. In particular, it is difficult to increase the rotating speed of the polygon motor which is already rotating at a fast speed. Thus, the driving speed of the LSU driving system is a major factor limiting the enhancement of the print speed of the LBP. For example, in the case wherein the LBP is capable of printing 20 pages per minute, the rotating speed of the polygon motor supports up to 20 pages per minute, so that printing more than 20 pages per minute cannot be performed. As such, in the conventional LBP, the print operation cannot be performed at a print speed greater than the print speed that the print engine can support.
Accordingly, a need exists for a printing system and method such that a print operation can be performed at a print speed greater than the print speed that the print engine can support.